Members of the Heracleum genus are hardy perennials that reach great heights of between 2.5 and 5.5 metres (8 to 17 feet).
They carry small white or pink flowers in umbels atop thick stems. They are ideal plants to grow in a wild flower garden or close to water.
Some common names for Heracleum include Cow Parsnip, Giant Hogweed, Cartwheel flower and Masterwort.
Heracleum sphondylium - Hog Weed by Mick E. Talbot.
Common Names: Hogweed, Giant Hogweed, Cow Parsnip, American Cow Parsley, Cartwheel Flower, Giant Masterwort.
Life Cycle: Hardy perennial.
Height: 110 to 144 inches (280 to 365 cm).
Native: Central Asia.
Growing Region: Zones 3 to 9.
When growing Cow Parsnips outdoors they should be prepared in the spring or autumn.
Spring sowing of Cow Parsnips is discussed here. The seeds should be sown in peat pots at a depth of 6 mm (1/4 inch) then the pots put in a black plastic bag, and placed in the the fridge for three weeks.
The pots should then be transferred and sank into a shady part of the garden, cover with glass.
Let the seedlings that appear grow until the autumn. Transplant the young Heracleum seedlings into a sunny or partially part of the garden. This should have a rich and moist soil.
As they are large plants, Heracleum should be spaced at about 1 to 1.25 m (40 to 50 inches) apart.
It is important to keep on top of Cow parsnips and other Heracleum Plants. They can spread rapidly and become invasive plants that will take over the garden given half a chance.
It is necessary to remove the flowering stems once they appear. Wear gloves when doing this as the leaves of the Heracleum plant are toxic, and may cause a skin rash. If you require more plants then they can be had by division, or just let them do their thing.